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Re: [TCML] The truth about LTR, STR, and resonant modes
So are you saying optimum power factor does play a role in max spark-length, given more power than a given coil can take?
Adam
--- On Wed, 5/28/08, DC Cox <resonance@xxxxxxxxxxxx> wrote:
> From: DC Cox <resonance@xxxxxxxxxxxx>
> Subject: Re: [TCML] The truth about LTR, STR, and resonant modes
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Date: Wednesday, May 28, 2008, 4:37 PM
> In addition to tuning the cap, we also tune the ballast and
> power supply
> with pole xmfrs to deliver the most efficient amount of
> current into the
> system for optimum spark production at any given voltage
> setting. We "dip"
> the supply current using our ballast control, and when the
> power factor is
> corrected back to 1.0 then you have max efficiency. Longer
> sparks occur
> when this setting is pushed up 10% but this does draw more
> current. Very
> similar to tuning a ham radio transmitter in which the
> operator "dips" the
> plate current to find the best resonant point before
> pushing higher power
> into the system. To do this properly one needs a power
> factor meter,
> however, lacking one, you can also do it by carefully
> monitoring your "plate
> current" and then adding 10% after the dip.
>
> Similar to what John is discussing.
>
> Dr. Resonance
>
> On Wed, May 28, 2008 at 12:34 PM, <Mddeming@xxxxxxx>
> wrote:
>
> >
> > Hi John,
> >
> > Exceptional clarity and conciseness. You definitely
> learned your writing
> > skills in the era before text-messaging. ;^)
> >
> > Matt D.
> >
> > In a message dated 5/28/08 2:21:00 A.M. Eastern
> Daylight Time,
> > FutureT@xxxxxxx writes:
> >
> > In a message dated 5/27/08 6:21:03 PM Eastern
> Daylight Time,
> > FutureT@xxxxxxx
> >
> > writes:
> >
> > > >If a pig or PT coil is run with a small
> > > >cap at high bps, then the ballast L has to be
> reduced to let in
> > > >more power (if long sparks are desired).
> Then the coil is truly
> > > >running in STR mode.
> > >
> > > >John
> > >
> >
> > Correcting my post above here. Such a coil as above
> > (small cap, high bps), is not necessarily STR mode.
> > This can be resonant or LTR mode also. It all
> depends on
> > the ballast setting (explained below). My other
> recent posts
> > mostly spoke of 120 bps operation but the comments
> > in those posts
> > apply to higher bps operation also, except the power
> > factor might not be as good at the higher bps.
> >
> > Deano is most likely correct that most folks are
> > probably running in resonant mode with their pig and
> > PT systems. Resonant mode is not solely dependent
> > on the cap value for a given non-shunted transformer.
> > Any cap value can be run in LTR, STR, or resonant
> > mode by adjusting the ballast as needed to give the
> > respective mode. This is mostly independent of
> > the transformer size (within reason of course). A
> > too large cap will not be able to be charged to
> > a reasonable voltage, etc.
> >
> > NST's (and OBITS), i.e. shunted, transformers are
> a
> > special case. For a given NST, a given cap value is
> > either LTR, STR, or resonant. This is not true for
> > unshunted transformers such as pigs and PT's.
> These
> > transformers are always run with a ballast. The
> > setting of the ballast will determine, along with the
> > cap value, whether the system is running in LTR,
> > STR, or resonant mode. The transformer doesn't
> > really enter into the equation except for impedance
> > transformation which determines how much ballast
> > L is needed for a particular mode, and also the
> > transformer must be able to handle the power, etc.
> >
> > It's not correct to say, "this pig has an
> LTR
> > value cap" or something similar. The cap itself
> > doesn't determine if the system is running in LTR
> > mode. This will be determined by the setting of
> > the ballast also. Of course the spark length has to
> > be considered. Longest sparks may be produced
> > in resonant mode, or slightly LTR. In resonant
> > mode, the reactance of the ballast
> "cancels" the
> > reactance of the cap, and this lets the maximum
> > power enter the system. This should give longest
> > sparks. LTR may work somewhat similarly up to
> > a point. There are issues such as inductive kick
> > to consider. As the ballast is increased in
> > inductance, this will create an LTR mode in
> > high bps systems, but it will also tend to
> > throttle back the power and reduce the spark
> > lengths.
> >
> > Coilers should select their cap value based on
> > the needed spark length, and the capabilities of
> > the transformer. If the transformer is extra
> powerful,
> > they can select a smaller cap, and adjust the
> > ballast for resonance or LTR and still get rather
> > short sparks if that's what they want. If they
> > want longer sparks, then just use a larger cap,
> > and again adjust for resonance or slight LTR. If one
> wants
> > super long sparks, then use an even larger
> > capacitor and again adjust for resonance or
> > slight LTR. This may force the pig to provide
> > double its rated power, but pigs can handle that.
> >
> > Folks used to talk a lot about each coil having
> > its own personality so to speak. I believe one
> > cause of that was the relative cap value versus
> > the transformer power versus the ballast setting,
> > thereby making the coil run either LTR, STR, or
> > resonant. I used to often talk about how
> > important it is to use the proper value cap for
> > 120 bps coils, but the proper value cap is
> > important for high bps coils too, so that the
> > spark lengths will be correct, when the ballast
> > is set (tuned) correctly. This is what Bill Wysock
> > talks about when he talks about tuning the ballast.
> > This is probably creating a resonant or slight LTR
> > condition for maximum efficiency and best power
> > factor. I'm not sure exactly what adjustment
> > (LTR, STR, or resonant) will give best power factor
> > with high bps, but surely one of them will be best
> > in that regard.
> >
> > In some cases folks may use a capacitor that
> > is larger than optimal for the desired spark length.
> > This may make it necessary to misadjust the
> > ballast and introduce inefficiency or a bad power
> > factor into the system to deliberately reduce the
> > spark length.
> >
> > Some may say that fixed LTR, STR, and resonant
> > cap values are valid for pigs and PT's. This
> > may be true if the transformer is run at its
> > rated power. But if it's not run at it's
> rated power,
> > if it's run at either higher or lower power, then
> > the LTR, STR, and resonant values change.
> > This is why it's best to look at it from both
> > and cap value *and* ballast inductance value
> > perspective. Otherwise the situation can be very
> > misleading.
> >
> > I hope the above is written clearly enough.
> > I kind of jumped around with the thoughts.
> >
> > John
> >
> >
> >
> >
> >
> >
> >
> >
> > **************Get trade secrets for amazing burgers.
> Watch "Cooking with
> > Tyler Florence" on AOL Food.
> >
> (http://food.aol.com/tyler-florence?video=4&?NCID=aolfod00030000000002)
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